1. Field of the Invention
The present invention relates to a telephone system and method for using time information transmitted at the beginning of phone calls to update the system time of a phone, other clocks, and computer systems.
2. Description of the Related Art
Telephone subscribers communicate via a vast telephone network, referred to as the Public Switched Telephone Network (PSTN). In the present disclosure, the term "PSTN" is intended to include the analog telephone network or POTS (Plain Old Telephone Service), ISDN (Integrated Services Digital Network), DSL (Digital Subscriber Line), and Wireless Local Loop (WLL), among others.
A telephone subscriber's communications devices, e.g., telephones, are typically connected in parallel to a telephone line which links a subscriber's premises to a telephone service provider's central office. An ordinary telephone is the most familiar of such communications devices. An ordinary telephone includes a handset, and the handset includes a receiver and a transmitter. The receiver is designed to be placed over a user's ear during use, and the transmitter designed to be positioned in close proximity to the user's mouth during use.
In a POTS system, when the telephone is not in use, the telephone is disconnected from the telephone line, except for a ringer circuit. When a caller places a telephone call to a receiving party, switching equipment in the central office transmits a series of ring signals over the receiving party's telephone line. The ring signals cause the ringer circuit of the receiving party's telephone to generate sounds which alert the receiving party to the incoming telephone call. At the same time, the switching equipment sends a series of ring-back signals to the caller to let the caller know that the telephone call is being placed. When the receiving party answers the incoming telephone call, a communication is established between the caller and the receiving party.
Several different types of communications devices are designed to automatically transmit or receive information following detection of one or more ring signals. Examples of such communications devices include telephone answering machines and communications devices equipped with modulator-demodulators (modems). An answering machine typically includes control circuitry which electrically connects a voice message unit to the telephone line after a predetermined number of ring signals are detected, causes the voice message unit to transmit (i.e., play back) a pre-recorded outgoing voice message, and then receives and records any incoming voice message transmitted by the caller following transmission of the outgoing voice message. Digital communications devices equipped with modems exchange frequency-encoded information via the telephone network. Facsimile (fax) machines are examples of such digital communications devices. A fax machine typically includes control circuitry which electrically connects a modem to a telephone line after a predetermined number of ring signals are detected, then either transmits or receives frequency-encoded digital information. A modulator portion of a modem within a transmitting fax machine converts a digital value (i.e., a logic one or a logic zero) to a corresponding analog tone. A demodulator portion of a modem within a receiving fax machine performs the opposite function, converting the analog tone to the corresponding digital value.
Telephone service providers also offer "caller ID" services which provide information about a caller. Devices which receive, store, and display digital caller ID information are widely available. The caller ID service is typically available to telephone subscribers for a small additional monthly fee. Under current standards, frequency-encoded digital caller ID information is transmitted between the first and second ring signals. Information about a caller is thus received, stored, and displayed by a caller ID device before a user would normally answer a ringing telephone. Caller ID information is typically recorded by caller ID devices whether the associated telephone is answered or not. Caller ID circuitry may be included as part of a telephone or the caller ID circuitry may be part of a separate box that is also connected to the telephone line.
A telephone system would be desirable that provides the user or the users with additional features for a more effective use of their telephone service. For example, one desirable feature for a telephone system would be a feature that could automatically update thesystem time of a phone or the time of a clock using the time from caller ID information. This would be advantageous after temporary power outages, especially so for phones and answering machines that are difficult to program.